A variety of fluorescent point defect centers in diamond have been identified that have potential applications in fields that include quantum information and biological imaging. In particular, the negatively charged nitrogen-vacancy (NV) center has attracted much interest. Demonstrated applications of NV centers include, without limitation, quantum information processing, super-resolution microscopy, Nano scale magnetometer using a single NV, and vector magnetic field imaging using ensembles of NVs.
For all of these applications, the photon collection efficiency is critically important.
Conventional methods of fluorescence detection typically result in photon collection efficiencies ηc of only about 10% or less. For example, a common limitation of experiments using color centers in diamond is the poor photon collection efficiency of microscope objectives due to refraction at the diamond interface. When detector coupling and quantum efficiencies are taken into account, photon detection efficiencies ηd of 2% or less are typical.